Microdynamical simulations of polyphase deformation and recrystallisation processes in polar ice and firn


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Ilka.Weikusat [ at ] awi.de

Abstract

The Antarctic and Greenland ice sheets store a significant amount of air within their upper, approximately thousand meters. Research shows how the presence of air inclusions can influence the microdynamical processes that affect the flow of ice (Azuma et al., 2012, Roessiger et al., 2014). The microdynamics of pure ice were successfully modelled by e.g. Montagnat et al. (2014) or Llorens et al. (2015), but studies taking into account second phases are scarce. Therefore, polyphase modelling was performed to focus on the implications of bubbles on recrystallisation and deformation. The full-field theory crystal plasticity code (FFT) of Lebensohn (2001), was coupled to the 2D multi-process modelling platform Elle (Bons et al., 2008), following the approach by Griera et al. (2013). FFT calculates the viscoplastic response of polycrystalline materials deforming by dislocation glide, taking into account mechanical anisotropy. Our models further incorporate surface- and strain-energy driven grain boundary migration and intracrystalline recovery. Sequential operation of each process for small time steps enables multi-process modelling of deformation and concurrent recrystallisation. Results show that air inclusions lead to increased strain localization and hence locally enhanced dynamic recrystallisation. This is in accordance with Faria et al. (2014), who theoretically predicted such localization, based on firn data from the EPICA Dronning Maud Land (EDML) deep ice core. Our results confirm that strain-induced grain boundary migration already occurs in the uppermost levels of ice sheets, as observed by Kipfstuhl et al. (2009) and Weikusat et al. (2009) in the EDML core. References Azuma, N., et al. (2012) Journal of Structural Geology, 42, 184-193 Bons, P.D., et al. (2008) Lecture Notes in Earth Sciences, 106 Faria, S.H., et al. (2014) Journal of Structural Geology, 61, 21-49 Griera, A., et al. (2013) Tectonophysics, 587, 4-29 Kipfstuhl, S., et al. (2009) Journal of Geophysical Research, 114, B05204 Lebensohn, R.A. (2001) Acta Materialia, 49, 2723-2737 Llorens, M.G., et al. (2015) submitted to Journal of Glaciology Montagnat, M., et al. (2014) Journal of Structural Geology, 61, 78-108 Roessiger, J., et al. (2014) Journal of Structural Geology, 61, 123-132 Weikusat, I., et al. (2009) Journal of Glaciology, 55, 461-472



Item Type
Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
Second Open Science Conference of the International Partnerships in Ice Core Sciences (IPICS2016), 07 Mar 2016 - 11 Mar 2016, Hobart, Australia.
Eprint ID
40936
Cite as
Steinbach, F. , Weikusat, I. , Bons, P. D. , Griera, A. , Llorens Verde, M. G. and Roessiger, J. (2016): Microdynamical simulations of polyphase deformation and recrystallisation processes in polar ice and firn , Second Open Science Conference of the International Partnerships in Ice Core Sciences (IPICS2016), Hobart, Australia, 7 March 2016 - 11 March 2016 .


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